Kechris, A. S. (1975) Countable ordinals and the analytical hierarchy, I. Pacific Journal of Mathematics, 60 (1). pp. 223227. ISSN 00308730. http://resolver.caltech.edu/CaltechAUTHORS:KECpjm75

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Abstract
The following results are proved, using the axiom of Projective Determinacy: (i) For n ≥ 1, every II(1/2n+1) set of countable ordinals contains a Δ(1/2n+1) ordinal, (ii) For n ≥ 1, the set of reals Δ(1/2n) in an ordinal is equal to the largest countable Σ(1/2n) set and (iii) Every real is Δ(1/n) inside some transitive model of set theory if and only if n ≥ 4.
Item Type:  Article  

Additional Information:  © 1975 Pacific Journal of Mathematics. Received August 29, 1974. Research partially supported by NSF grant GP 27964.  
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Record Number:  CaltechAUTHORS:KECpjm75  
Persistent URL:  http://resolver.caltech.edu/CaltechAUTHORS:KECpjm75  
Alternative URL:  http://projecteuclid.org/Dienst/UI/1.0/Summarize/euclid.pjm/1102868636  
Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided.  
ID Code:  841  
Collection:  CaltechAUTHORS  
Deposited By:  Tony Diaz  
Deposited On:  19 Oct 2005  
Last Modified:  22 May 2013 22:57 
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